1. Field of the Invention
This invention relates generally to assay methods in which a member of a specific binding pair can be detected and quantified by means of an optically detectable reaction brought about by the enzymolysis of an enzyme-cleavable group in a 1,2-dioxetane molecule. The invention relates specifically to the production of 1,2-dioxetanes and their intermediates useable in such assay methods.
2. Description of Related Art
1,2-Dioxetanes, cyclic organic peroxides whose central structure is a four-membered ring containing a pair of contiguous carbon atoms and a pair of contiguous oxygen atoms (a peroxide linkage), are a known, but heretofore seldom utilized, class of compounds. Because of their inherent chemical instability, some 1,2-dioxetanes exhibit chemiluminescent decomposition under certain conditions, e.g., by the action of enzymes, as described in copending, commonly-assigned Bronstein, U.S. patent application Ser. No. 889,823 entitled "Method of Detecting a Substance Using Enzymatically-Induced Decomposition of Dioxetanes", and in copending, commonly assigned Bronstein, et al., U.S. patent application Ser. No. 140,035 entitled "Dioxetanes for Use in Assays", the disclosures of which are incorporated herein by reference. The amount of light emitted during such chemiluminescence is a measure of the concentration of a luminescent substance which, in turn, is a measure of the concentration of its precursor 1,2-dioxetane. Thus, by measuring the intensity and duration of luminescence, the concentration of the 1,2-dioxetane (and hence the concentration of the substance being assayed, i.e., the species bound to the 1,2-dioxetane member of the specific binding pair) can be determined. The appropriate choice of substituents on the 1,2-dioxetane ring allows for the adjustment of the chemical stability of the molecule which, in turn, affords a means of controlling the onset of chemiluminescence, thereby enhancing the usefulness of the chemiluminescent behavior of such compounds for practical purposes, e.g., in chemiluminescence immunoassays and DNA probe assays.
The preparation of 1,2-dioxetanes by photooxidation of olefinic double bonds is known. However, a need exists for a convenient, general synthesis of substituted 1,2-dioxetanes from olefinically unsaturated precursors derived from readily available or obtainable starting materials through tractable intermediates. In this connection, a particular need exists for a commercially useful method for producing substituted 1,2-dioxetanes of the formula: ##STR2## wherein T, R, Y, and Z are defined herein below, from enol ether-type precursors: ##STR3##
Enol ethers can be prepared by several classical methods, for example, by acid-catalyzed elimination of alcohol from acetals [R. A. Whol, "Synthesis", p. 38 (1974)], by Peterson or Wittig reactions of alkoxymethylene silanes or phosphoranes with aldehydes or ketones in basic media [Magnus, P. et al., Organometallics, 1, 553 (1982)], and by reactions of alkoxyacetic acid dianions with ketones followed by propiolactone formation and elimination of CO.sub.2 [Caron, G., et al., Can. J. Chem., 51, 981 (1973)]. The O-alkylation of ketone enolate anions is less often used as a general preparative method due to the variable amounts of concomitantly formed alpha-alkylated ketones, the extent of which depends on the solvent, base, alkylating agent and ketone structure (see, H. O. House, "Modern Synthetic Reactions" pp. 163-215 (Benjamin, 1965); and J. D. Roberts and M. C. Caserio, "Basic Principles of Organic Chemistry" (Benjamin, 1964)). With the use of hexamethyl phosphoramide (HMPA), a known carcinogenic solvent, it is, at best, possible to obtain yields of the O-alkylation product which are no higher than 70%. Moreover, the separation of enol ether from the C-alkylated ketone is quite tedious.